The estimation of the number of various leukocytes in blood and other body fluids is one of the most widely used tools in medicine. The traditional way of obtaining this information is the counting and differentiating of the cells under the light microscope. This technique is complemented by the automated counting in cell counters based on the principle of counting the number of particles in the fluid and the measurement of various physical parameters such as size, forward and side scatter, but also my histochemical staining of cells. An extension of these techniques is the flow cytometer principle in which antibodies are used to identify individual cells based on their cell surface antigens or by means of their content of intracellular antigens after permeabilisation of the cells.
In WO 00/58726 there is described a method for quantitating leukocyte count in whole blood. However, this method does not quantitate different specific subtypes of leukocytes in respect of number or ratio.